Generally, in a design stage of producing goods, by varying values of plural design parameters so as to minimize plural kinds of costs (also called “objective function”), optimum values of the plural design parameters are determined. However, in such multi-objective optimization design, generally, an optimum solution is not uniquely determined, and the trade-off relationship occurs among the costs. In other words, pareto optimum solutions are obtained.
Therefore, in the multi-objective optimization design, it is difficult to understand the relationship between the design parameters and the costs, and this causes a problem when a designer determines the optimum solutions of the design parameters. Especially, it is difficult to see changes of the design parameter values, which correspond to changes of the costs in a cost space that is mapped by plural kinds of costs.
In order to deal with this problem, a technique to show changes of the design parameters in a design parameter space when moving between 2 points (e.g. A and B) on a pareto curve in the cost space exists. In this technique, points P and Q in the design parameter space, which correspond to the points A and B on the pareto curve, are derived to extract a point R corresponding to a point on the pareto curve in the cost space among points on a perpendicular bisector to a segment connecting the points P and Q. In the following, the similar processing is carried out for a segment connecting the points P and R and a segment connecting the points R and Q, and when such a processing is further repeated so as to fragment the segments, it is possible to grasp the changes of the design parameters in the design parameter space when moving between the points A and B on the pareto curve. However, according to this method, the search in the design parameter space is limited to the perpendicular bisector. Therefore, this technique cannot deal with a case where there are plural routes in the design parameter space and a case where the route branches off on the way and/or plural routes are merged into one route. Furthermore, there is a problem that only the route on the pareto curve can be handled.
Moreover, a following technique exists. Namely, points in a predetermined region in the design parameter space are arranged in gridlike fashion, and corresponding points in the cost space are calculated. Then, when a designer designates a point or region in the cost space, a corresponding point or region in the design parameter space is shown. However, any idea that a route in the cost space is designated does not exist.
In the aforementioned techniques, it is impossible to grasp how values of the design parameters change when increasing or decreasing specific costs in the cost space, or grasp what condition of the design parameters should be eased in order to carry out design having better cost values regardless of the present feasible region. Specifically, it is not possible to grasp any corresponding route in the design parameter space when designating an arbitrary route in the cost space.